Hip Joint
The hip joint is a ball-and-socket joint that represents the articulation of the bones of the lower limb and the axial skeleton (spine and pelvis). The rounded femoral head sits within the cup-shaped acetabulum. The acetabulum is united by the three bones of the pelvis (the ischium, ilium and pubis). Between them is a Y-shaped cartilaginous growth plate. The acetabulum covers nearly half of the femoral head. The articulation is deepened by the labrum, a fibrocartilaginous lip that extends around the acetabulum an crosses the equator of the femoral head. Motion * Flexion: ilipsoas, rectus femoris * Extension: hamstrings * Abduction: gluteus minimus and medius * Adduction: adductors muscles * External rotation: obturator internus, gemelli, piriformis and gluteus maximus * Internal rotation: gluteus minimus and medius Acetabulum * Acetabular fossa: Central cartilage devoid region * Acetabular notch: Osseous opening inferior margin with no cartilage. ** Covered by synovium: Extra-articular * Anterior & posterior rims: Osseous margins of acetabulum Labrum * Fibrocartilage * Resides on acetabular rim * Vascular supply: Branches obturator, superior & inferior gluteal arteries * Function ** Protect cartilage: Distributes forces by maintaining synovial fluid layer between articular surface ** Prevents lateral translation femoral head Femoral Head * 2/3 of sphere * Covered by articular cartilage ** Except central fovea capitis ** Cartilage thickest superiorly * Fovea capitis: Central cartilage devoid depression on head. Attachment site for ligamentum teres Relations * anteriorly: iliopsoas and femoral vessels * posteriorly: sciatic nerve and obturator internus with gemelli muscles * superiorly: gluteus minimus and medius * inferiorly: pectineus and obturator externus Joint Capsule * 2 layers: Internal synovial; external fibrous ** External forms capsular ligaments * Attachments ** Acetabulum - circumferential around the labrum ** Femur *** Anterior: Intertrochanteric line *** Posterior: mid way femoral neck *** Anterior attachment more lateral than posterior attachment *** Fibres reflect back as retinacular fibres that blends with the periosteum. * External layer: Ligaments of joint capsule ** Iliofemoral (Bigelow ligament) *** Anterior, superior longitudinal spiral *** Inverted Y-shape *** Prevents hyperextension *** Strongest ligament in body *** Medial attachment anterior inferior iliac spine ** Pubofemoral: Anterior, inferior, longitudinal spiral *** Prevents hyperabduction *** Medial attachment obturator crest pubis ** Ischiofemoral: Posterior, longitudinal spiral *** Weakest * Synovial layer ** lines all the capsules and the articular surfaces including the fovea and the circumference of the labrum * Ligamentum Teres ** Attachments: Fovea capitis & transverse ligament ** Lined by synovium: Intracapsular, extra-articular ** Artery of ligamentum teres which is essentially negligible. * Transverse Ligament ** Spans acetabular notch *** Completes socket of acetabulum ** Blends with labra at margins of notch *** Labroligamentous sulci at junction Arterial supply * Trochanteric anastomoses receiving supply from multiple branches, but mainly the medial circumflex artery. These run along the neck beneath the retincular fibres. * Femoral head mainly receives fro medial and lateral circumflex femoral and artery of ligamentum teres (branch of posterior division of obturator artery) * Superior and inferior gluteal arteries offer descending branches to the trochanteric anastomoses. Venous drainage * follows arterial supply Innervation * Branches from nerve to rectus femoris (femoral), nerve to quadratus femoris (sciatic), anterior division obturator nerve, accessory obturator nerve, superior gluteal nerve. Variant: * Perilabral sulci * Sublabral recess * Enostosis (bone island) * Allen's fossa (small cervical depression by NOF) * Os acetabuli (ossicle in the upper rim of the acetabulum)